Porcelain enameling process



Oct. 9, 1951 E. R. ZADEMACH ET AL PORCELAIN ENAMELING PROCESS Filed Feb. 14, y 1947 Patented Oct. 9, 1951Y UNITED STATES PATENT OFFICE PORCELAIN ENAMELING PROCESS Erich R. Zademach and William W. Clarke, Hillside, N. J., assignors to Metalwash Machinery Company, Irvington, N. J., a copartnership Application February 14, 1947, Serial No. 728,414

4 Claims. 1

The present invention relates to a method and apparatus for cleaning, pickling and nickel plating metal parts in preparation for the porcelain enameling thereof.

It has been the practice after metal parts have been cleaned and pickled, to immerse them in a bath of nickel sulphate solution to form thereon a coating of nickel to which the enamel is subsequently bonded. Hitherto, it was the common belief of the art that a good effective nickel coating to which enamel would strongly adhere could not be deposited on a metal object by any process except an immersion process.

One object of the present invention is to provide a new and improved process and apparatus for depositing a nickel coating on metal parts in preparation for the porcelain enameling thereof.

Another object is to provide a continuous process and apparatus by which metal parts may be effectively and quickly cleaned, pickled and nickel coated in preparation for porcelain enameling.

In accordance with certain features of the present invention, a nickel salt solution, such as that of nickel sulphate, is sprayed on the metal parts after they have been cleaned and pickled. It is found by actual impact tests, that the coating of nickel deposited on the metal parts by this spray process is such as to cause the porcelain enamel subsequently applied to said parts to adhere more strongly thereto, than in the case of a nickel coating applied by the immersion process.

As a further feature, the spraying of the nickel sulphate solution or other nickel depositying salt solution on the metal parts is combined with the spraying of the cleaning, pickling and rinsing liquids in successive stages in a continuous process and apparatus, thereby attaining maximum production capacity. Furthermore, with a continuous process and apparatus as described, the apparatus can be set to operate uniformly on all metal parts, without being affected by the operators discretion, as in the case of a discontinuous immersion process or apparatus. All metal parts, therefore, will receive uniform treatment, and will be uniform in character when subjected to the porcelain enameling process. Furthermore, this process and apparatus not only results in superior cleaning, but since the air in the spaces between the operations in the apparatus is in liquid or vapor saturated condition, the Work cannot dry out between the various treatments or stages, nor is it contaminated by being drawn up through the slime on the surfaces of the immersion tanks.

Various other objects, features and advantages of the invention will be apparent from the following particular description, and from an inspection of the accompanying drawings, in which:

Fig. l is a top plan view Somewhat diagrammatic of the improved apparatus which embodies the present invention, and which can be employed to carry out the process of the present invention; and

Fig. 2 is a diagrammatic transverse Section of the apparatus taken on line 2-2 of Fig. 1.

Referring to the drawings, there is provided a long treating chamber or tunnel I0, shown in the form of a J, to suit the available floor space, and having an opening or slot Il in the roof l2 thereof extending along the length of said cham'- ber. Extending along the top of the tunnel l0 over the slot Il are the runs of an endless horizontal rail conveyor I3. Supported from this conveyor I3 and rolled along the rail thereof are hangers l5 from which the metal parts I6 to be treated are suspended. These metal parts I6, which are usually of iron, are shown in the form of flat plates, but it must be understood that as far as certain aspects of the invention are concerned, these may be of any suitable shape..

The tunnel or chamber l!) isdivided into different compartments by partitions I8 having openings 2U through which the metal parts are continuously advanced edgewise. Suitable ventilators i9 are provided for the tunnel in the form of openings in the roof, especially between the spraying regions of the compartments.

The metal parts I6 are introduced into the tunnel I0 from the entrance end 2| thereof, and are advanced continuously therealong until they are discharged from the exit ends 22 thereof. As the metal parts are continuously advanced through the tunnel I0, they are subjected to different cleaning, pickling nickel plating and drying stages in sequence, as will be described.

Near the entrance end of the tunnel l!) is a compartment A, in which each metal part IB is sprayed with a hot emulsion wash from two sets of spray units 23, located on opposite sides of the path of travel of said metal part. Each of these spray units 23 consists of a plurality of vertical headers having spray nozzles in the inner sides thereof, spaced therealong to project the spray jets 24 against the advancing metal object I6. The circulating system for the spray units 23 in theicompartment A comprises a sump tank 25 into which the sprayed solution is drained,

'and from which the spray solution is recirculated to the spray nozzles by a pump 26.

The hot emulsion spray wash in the compart- Vment A removes the surface dirt and grease from the metal part I5, and comprises a suitable cleansing liquid, as for example, a mixture of kerosene and water containing cresylic acid or other appropriate emuls'ifying agent.

The metal work object I6 then advances into compartment B where said object is subjected to a fresh water spray rinse from spray units 21 on opposite sides thereof similar to those in compartment A, in order to Wash off the dirt, grease and emulsifying liquid from the previous opera--y tion in compartment A. The fresh water is delivered to these spray units 21 by a feed line 28, and the spent water is drained to sewer by a discharge line 29.

The operation in compartment B may leave `an oil film on the metal object. To remove this oil film, the metal object I6 is subjected to a hot alkali spray wash in compartment C from spray units 30 located on opposite sides o'f the course of said metal part, as in compartment A, and fed by a recirculating system comprising a sump tank 3l and a circulating pump 32 connected on its suction side to said tank, and on its discharge side to said spray units.

The metal object 'l5 then moves into the compartments D, where it is subjected to a threestage Ywater rinse to remove the residual alkali therefrom. In this compartment D, there are three groups of spray units 34, 35 and 35, each comprising a pair of or two sets of vertical headers on opposite sides of the path of travel of the metal object, and each carrying a series of spray nozzles. The first group `of spray units 34 supplies recirculated rinse vby means of a pump 40 from a recirculating sump tank 38 underneath the spray units 35 and 36, so that most of the Aresidual alkali wash is removed from the metal object I6. The spent rinse water from the spray units 34 is drained to the sewer through a discharge line 31. The second group of spray units 35 supplies recirculated rinse water from the sump recirculating tank 38 by means of the pump 40, and the drain from said spray units is returned to said tank.

Clean fresh water from a supply line 4I is delivered to the third group of spray units 36 for a nal rinse of the metal object I6, and is drained into the sump tank 38. This clear water rinse is controlled, so that it makes up the amount of water diverted and drained to sewer by the first group of spray units 34.

Alter rinsing in the compartment D, the metal object l moves into the compartment E, where it is subjected to the action of a hot pickling liquid, which is desirably 1'0 to 15% sulphuric acid solution. This sulphuric acid solution in the compartment E is sprayed on to the advancing metal object I6 -by two sets of spray units 43, which are located on opposite sides of the path of travel of said object, and which are similar in construction to the other spray units described. The hot sulphuric acid solution is recirculated through the spray units 43 by a sump tank 44 and a pump 45.

The metal object then advances into the com- .partments F', which are similar tothe compartments D, and in which the metal part is subjected to a three-stage water rinse as in said lat- .ter compartments.

The metal object after being thoroughly washed in the compartment E, travels into compartment G. In this compartment, the metal object I6 is subjected to a spray of a solution of a nickel salt of a character which has an anion capable of reacting with the ferrous metal of the object I6, to deposit a coating of pure nickel on to said object. The liquid usually employed for that purpose is nickel sulphate solution. This nickel sulphate solution is sprayed in the'form of a mist on to the metal object i6 as it travels through the compartment G. The pressure of the solution in the spray headers may be between eight and ten pounds per square inch.

For the purpose of spraying the nickel sulphate solution on to the metal object I6, there are provided two sets of spray units 50 disposed on opposite sides of the course of travel of said object. Each of the spray units 5D comprises a series of substantially vertical headers 5l spaced along the compartment G, and interconnected by a feed line 52 on the discharge side of a recirculating pump 53, -thersuction side thereof being connected Vto a sump tank 54 at the bottom of the compartment, and in position to receive the drain from the spray units 50.

The nickel sulphate solution may be of any suitable strength, and may, for example, have Aa concentration of about two ounces of the hydrated sulphate NiSO4.6H2O to one gallon of water or the equivalent of .448 ounce of nickelV per gallon. The temperature of the nickel sulphate solution is approximately 175 F., and its pH is from 3 to 3.5. T-he'metal object I6 may travel at a rate of ve to ten feet per minute through the compartment G, and the time required to traverse said compartment may take from three to five minutes, during which time the metal object I6 isV sub-Il jected to the spray of hot nickel sulphate solution. As a result of this operation, a coating of pure nickel is deposited on the surface of the metal object I6. This v.nickel coating will be `of uniform `thickness throughout the area of the metal object I 6, and its characteristics will be predetermined according to the shape and size of the metal object, speed of travel thereof through the compartmentV G, the concentration and temperature of the hot nickel sulphate solution, and other factors, all of which may be easily controlled. It is found, for example, that for a nickel sulphate spraying period of three minutes, there will, under certain conditions, be deposited a nickel layer at the rate of .05 grams per square foot, and for a nickel sulphating period of five minutes, the nickel deposit will be at the rate of about .08 grams per square foot.

The metal object I6 after having the coating of nickel formed thereon by the spraying process described, passes through compartments H, Where it is subjected to a three-stage water rinse spray, as in compartmentsD and F.

From the .compartment the metal object I6 travels into compartment I, Where it is subjected to a neutralizing spray to Vremove lany residual acid thereon. The spraying in the compartment I is effected through two sets of spray units 56 disposed on opposite sides of the course of travel of .the metal object l5, as in the other compartments, and the neutralizing solution is circulated through said spray units by means of a sump tank 51 and a pump 58. The neutralizing spray solution may consist of a combination of sodium carbonate and borax. The metal object I5 then travels into the nal compartment J, where it is subjected to a hot blast from a series vof hot air blast units on opposite sides of the metal object. The air for the pur,-

Time and temperature schedule Temperature Tune F. Minutes (A) Emulsion wash 180 1% (B) Water rinse.. Cold (C) lukas wash iso 1% 20 (D) Water rinse. Cold 1 (E) Sulphuric ac 160 2% (F) Water rinse Cold 1 (G) Nickel sulphate spray 175 3 (H) Water rinse Cold 1 (I) N eutralizing 180 (J) Air blast drying 220 5 It should be noted from the above schedule of operations, that the periods of the various cycles are very much shorter than is the case with the usual type of immersion cleaning, pickling and nickel sulphating. Nevertheless, the cleaning results obtained are much superior to those obtained in the usual immersion processes. Furthermore, it has been shown by actual tests, that the enamel will adhere more strongly to the nickel coating deposited by the spray process than by the usual immersion process.

While the invention has been described with particular reference to a specific embodiment, it is to be understood that it is not to be limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims.

-improvement which comprises conveying a substantially vertically disposed ferrous object through a directed mist of an aqueous solution of a nickel salt having an anion capable of unitgravity flow.

2. In a process for porcelain enameling a ferrous object in which a layer of nickel is first deposited thereon and the porcelain enameling subsequently formed on said nickel layer, the improvement which comprises conveying a substantially vertically disposed ferrous object through a directed mist of an aqueous solution of a nickel salt having an anion capable of uniting with the metal in said object, said object being subjected to said mist for a period of at least three minutes, and draining the excess solution from said object by gravity 110W.

3. In a process for porcelain enameling a ferrous object in which a layer of nickel is first deposited thereon and the porcelain enameling subsequently formed on said nickel layer, the improvement which comprises conveying a substantially vertically disposed ferrous object through a directed mist of an aqueous solution of a nickel salt having an anion capable of uniting with the metal in said object, and. draining the excess solution from said object by gravity flow.

4. In a process for porcelain enameling a ferrous object in which a layer of nickel is rst deposited thereon and the porcelain enameling subsequently formed on said nickel layer, the improvement which comprises conveying a ferrous object through a directed mist of an aqueous solution of a nickel salt having an anion capable of uniting with the metal in said object, and draining the excess solution from said object by gravity flow.

ERICH R. ZADEMACH. WILLIAM W. CLARKE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,064,173 McGohan Dec. 15, 1936 2,265,467 Alexander Dec. 9, 1941 2,279,686 Kerlin Apr. 14, 1942 

1. A PROCESS FOR PORCELAIN ENAMELING A FERROUS OBJECT IN WHICH A LAYER OF NICKEL IS FIRST DEPOSITED THEREON AND THE PORCELAIN ENAMELING SUBSEQUENTLY FORMED ON SAID NICKEL LAYER, THE IMPROVEMENT WHICH COMPRISES CONVEYING A SUBSTANTIALLY VERTICALLY DISPOSED FERROUS OBJECT THROUGH A DIRECTED MIST OF AN AQUEOUS SOLUTION OF A NICKEL SALT HAVING AN ANION CAPABLE OF UNITING WITH THE METAL IN SAID OBJECT, SAID OBJECT BEING SUBJECTED TO SAID MIST FOR A PERIOD OF AT LEAST THREE MINUTES, SAID AQUEOUS SOLUTION BEING AT A TEMPERATURE OF APPROXIMATELY 175* F., AND DRAINING THE EXCESS SOLUTION FROM SAID OBJECT BY GRAVITY FLOW. 